<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    table{
      border:1px solid #000;
      border-spacing: 0;
      width: 415px;
      height: 415px;
      margin: 50px auto;
    }
    td{
      border: 1px solid #000;
      height: 30px;
      width: 30px;
    }
  </style>
</head>
<body>
<table>
  <tr>
    <td colspan="12">1</td>
    <td rowspan="12">2</td>
  </tr>
  <tr>
    <td rowspan="12">4</td>
    <td colspan="10">5</td>
    <td rowspan="10">6</td>
  </tr>
  <tr>
    <td rowspan="10">8</td>
    <td colspan="8">9</td>
    <td rowspan="8">10</td>
  </tr>
  <tr>
    <td rowspan="8">12</td>
    <td colspan="6">13</td>
    <td rowspan="6">14</td>
  </tr>
  <tr>
    <td rowspan="6">16</td>
    <td colspan="4">17</td>
    <td rowspan="4">18</td>
  </tr>
  <tr>
    <td rowspan="4">20</td>
    <td colspan="2">21</td>
    <td rowspan="2">22</td>
  </tr>
  <tr>
    <td rowspan="2">24</td>
    <td>25</td>
  </tr>
  <tr>
    <td colspan="2">23</td>
  </tr>
  <tr>
    <td colspan="4">19</td>
  </tr>
  <tr>
    <td colspan="6">15</td>
  </tr>
  <tr>
    <td colspan="8">11</td>
  </tr>
  <tr>
    <td colspan="10">7</td>
  </tr>
  <tr>
    <td colspan="12">3</td>
  </tr>
</table>
</body>
</html>